Cooling fan

ABSTRACT

A cooling fan includes a base forming a central tube at a central portion thereof, a stator mounted around the central tube and a rotor rotatable relative to the stator. The central tube defines at least one engaging slot therein. The stator includes a stator core, an upper insulating frame attached to a top side of the stator core and a lower insulating frame attached to a bottom side of the stator core. The upper insulating frame forms a plurality of protrusion tabs extending inwardly from an inner circumferential surface of the upper insulating frame. The protrusion tabs extend into and engage in the at least one engaging slot to securely mount the stator core around the central tube.

BACKGROUND

1. Technical Field

The present disclosure relates to a cooling fan, and particularly to a cooling fan having a stator firmly mounted thereon.

2. Description of Related Art

With continuing development of electronic technology, heat-generating electric components such as CPUs (central processing units) are generating more and more heat which requires immediate dissipation. Cooling fans are commonly used in combination with heat sinks for cooling the CPUs.

A typical cooling fan includes a fan housing forming a base at a central portion thereof, a stator mounted on the base and a rotor rotatably supported by the stator. The stator is mounted around a central tube formed at a central portion of the base and stuck to the central tube with glue. However, the glue cannot firmly secure the stator on the central tube. For example, the cooling fan may suffer a crash during transportation which may result in a separation of the stator from the central tube.

Therefore, a cooling fan is desired to overcome the above described shortcoming.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a cooling fan in accordance with an exemplary embodiment.

FIG. 2 is an exploded, isometric view of a stator and a central tube of a fan housing of the cooling fan of FIG. 1, with a circuit board and coils being removed from the stator for clarity.

FIG. 3 is a top plan view of the stator of FIG. 2, also with the circuit board and the coils being removed for clarity.

FIG. 4 is an enlarged view of a portion of the cooling fan of FIG. 1, in which the stator is to be mounted to the central tube.

FIG. 5 is an enlarged view of a circled portion V of FIG. 1, in which the stator has been mounted to the central tube.

FIG. 6 is a view similar to FIG. 2, with the central tube of the fan housing of the cooling fan being modified.

DETAILED DESCRIPTION

FIG. 1 shows a cooling fan 100 in accordance with an exemplary embodiment of the disclosure. The cooling fan 100 includes a fan housing 10, a stator 20 and a rotor 30 received in the fan housing 10.

The rotor 30 includes a cylindrical hub 32 and a plurality of blades 38. The hub 32 includes a top wall 322 and a sidewall 324 extending downwardly from a circumferential edge of the top wall 322. A shaft 34 extends downwardly from a central portion of the top wall 322 and forms a free end 343. The blades 38 extend radially and outwardly from an outer periphery of the sidewall 324 of the hub 32.

The stator 20 includes a PCB 26 (printed circuit board), a stator core 22, upper and lower insulating frames 28, 29, and a plurality of stator coils 24. The upper and lower insulating frames 28, 29 are attached to top and bottom sides of the stator core 22, respectively. The stator coils 24 are wound on the upper and lower insulating frames 28, 29 and around the stator core 22. Thus, the stator coils 24 are electrically separated from the stator core 22 by the upper and lower insulating frames 28, 29. The PCB 26 is attached to a bottom side of the lower insulating frame 29 and electrically connected with the stator coils 24 to control an electrical current flowing through the stator coils 24.

Referring to FIGS. 2 and 3, the stator core 22 includes an annular body 222 defining a through hole 40 therein and a plurality of claws 224 extending radially and outwardly from an outer periphery of the annular body 222. Each claw 224 has a T-like shape and includes an arced wing 226 formed at a distal end thereof. The claws 224 are spaced from each other and evenly arranged around the annular body 222 along a circumferential direction of the annular body 222. The wings 226 are arranged on an imaginary circle around the annular body 222. Every two neighboring claws 224 and a corresponding portion of the annular body 222 between the two neighboring claws 224 cooperatively define a winding slot 228 thereamong.

The upper insulating frame 28 has an outline corresponding to a profile of the stator core 22. The upper insulating frame 28 includes a main body 282 corresponding to the annular body 222 of the stator core 22 and a plurality of protecting arms 284 corresponding to the claws 224 of the stator core 22. The main body 282 is annular and defines a through hole 40 therein. The main body 282 has an inner diameter greater than that of the annular body 222 of the stator core 22. The protecting arms 284 each are generally T-shaped. The protecting arms 284 extend radially and outwardly from an outer circumferential surface of a bottom edge of the main body 282. The main body 282 and the protecting arms 284 form a plurality of flanges 286 at edges thereof. The flanges 286 extend downwardly from the edges of the main body 282 and the protecting arms 284 into the winding slots 228 of the stator core 22, when the upper insulating frame 28 is attached to the stator core 22.

A plurality of protrusion tabs 281 extend inwardly from an inner circumferential surface of the bottom edge of the main body 282 in an opposite direction to the protecting arms 284. The protrusion tabs 281 are evenly arranged along a circumferential direction of the main body 282 and protrude inwardly into the through hole 40 of the upper insulating frame 28. Inner free ends of the protrusion tabs 281 cooperatively define an imaginary circle which has a diameter slightly smaller than the inner diameter of the annular body 222 of the stator core 22. Each protrusion tab 281 is substantially trapezoid-shaped and aligned with a corresponding protecting arm 284. Each protrusion tab 281 includes an outer end connected with the main body 282. The inner free end of each protrusion tab 281 is located in the through hole 40 of the upper insulating frame 28.

The lower insulating frame 29 has a configuration similar to the upper insulating frame 28. The lower insulating frame 29 also includes a main body 292 located at a central portion and a plurality of protecting arms 294 extending radially and outwardly from an outer circumferential surface of the main body 292. The main body 292 also defines a through hole 40 therein. The through holes 40 of the annular body 222 of the stator core 22 and the main bodies 282, 292 of the upper and lower insulating frames are aligned with each other to cooperatively define a mounting hole 50 through the stator 20 along an axial direction thereof. A plurality of flanges 296 extend upwardly from edges of the main body 292 and the protecting arms 294 for inserting into the winding slots 228 of the stator core 22. The lower insulating frame 29 differs from the upper insulating frame 28 only in that the lower insulating frame 29 does not form the protrusion tabs 281.

The upper insulating frame 28 is attached to the top side of the stator core 22, with the flanges 286 extending into the winding slots 228 to cover an upper portion of the stator core 22. The protrusion tabs 281 of the upper insulating frame 28 are located on the annular body 222 of the stator core 22 with outer ends of the protrusion tabs 281 rested on the annular body 222 and the inner free ends of the protrusion tabs 281 protruding inwardly beyond the annular body 222 into the through hole 40 of the stator core 22. The lower insulating frame 29 is attached to the bottom side of the stator core 22. The flanges 296 of the lower insulating frame 29 extend into the winding slots 228 to cover a lower portion of the stator core 22. The stator coils 24 are wound on the protecting arms 284, 294 of the upper and lower insulating frames 28, 29, and electrically insulated from the stator core 22 by the upper and lower insulating frames 28, 29.

Referring back to FIG. 1, the fan housing 10 includes a square-shaped hollow casing 12, a base 14 arranged at a central portion of the casing 12 and a plurality of ribs 16 connecting the base 14 to the casing 12. The fan housing 10 defines an air outlet 17 at a top side and an opposite air inlet 18 at a bottom side thereof. The base 14 is located at a center of the air inlet 18. A central tube 15 extends upwardly from a central portion of the base 14 towards the air outlet 17 for mounting the stator 20 thereon. The casing 12, the base 14 and the ribs 16 can be made of plastic material and integrally formed by plastic injection molding. The central tube 15 may be made of metal or plastic material. In this embodiment, the central tube 15 is made of copper. The central tube 15 is preformed first and then connected with the base 14 by insert molding technique, during the formation of the casing 12.

Referring to FIG. 2, the central tube 15 is column-shaped and defines a through hole 150 therein along an axial direction thereof. The central tube 15 includes a main section 154, a fixing section 152 formed at a top end of the main portion 154 and a securing section 156 formed at a bottom end of the main section 154. The fixing section 152 has a diameter smaller than that of the main section 154, whereby a step 159 is formed between the fixing section 152 and the main section 154. The diameter of the main portion 154 is smaller than that of the securing section 156. The diameter of the fixing section 152 is equal to the diameter of the through hole 40 of the annular body 222 of the stator core 22, such that the fixing section 152 can extend through the stator core 22 to mount the stator 20 around the central tube 15. A chamfer 157 is formed at a top end of the fixing section 152. An annular engaging slot 155 is defined around an outer circumferential surface of the fixing section 152 under the chamfer 157. The engaging slot 155 is recessed inwardly from the outer circumferential surface of the central tube 15 for extension of the inner free ends of the protrusion tabs 281 of the upper insulating frame 28 therein. The diameter of the central tube 15 at the engaging slot 155 is not larger than that of the imaginary circle cooperatively defined by the inner free ends of the protrusion tabs 281.

An annular top flange 153 extends outwardly from an outer circumferential surface of a top end of the securing section 156, and an annular bottom flange 151 extends outwardly from an outer circumferential surface of a bottom end of the securing section 156. The top and bottom flanges 153, 151 are parallel to and spaced from each other. Thus, the securing section 156 is located between the top and bottom flanges 153, 151. The top and bottom flanges 153, 151 each have a diameter greater than that of the securing section 156. The base 14 has a portion (not labeled) extending into a space between the top and bottom flanges 153, 151 to engage with the securing portion 156 of the central tube 15, thereby securing the base 14 and the central tube 15 together. A top surface of the top flange 153 and a bottom surface of the bottom flange 151 are respectively coplanar to top and bottom surfaces of the base 14, to enhance a connection of the central tube 15 and the base 14 and prevent the central tube 15 from separating from the base 14.

An inner annular flange 158 extends inwardly from an inner circumferential surface of a middle portion of the central tube 15. A pair of bearings 80 are received in the through hole 150 of the central tube 15. The top bearing 80 abuts a top surface of the annular flange 158. A spring (not labeled) is sandwiched between a bottom surface of the annular flange 158 and the bottom bearing 80.

Referring to FIGS. 4 and 5, in assembly of the cooling fan 100, the stator 20 is pressed downwardly around the central tube 15 during which the fixing section 152 of the central tube 15 extends sequentially through the PCB 26, the lower insulating frame 29, the stator core 22 and the upper insulating frame 28 of the stator 20. As an inner diameter of each of the PCB 26, the lower insulating 29 and the stator core 22 is not smaller than the diameter of the fixing section 152 of the central tube 15, the fixing section 152 can extend through the PCB 26, the lower insulating frame 29 and the stator core 22 easily. However, when the stator 20 continuously moves downwardly, the inner free ends of the protrusion tabs 281 abut against the chamfer 157 of the fixing section 152 of the central tube 15 because the diameter of the imaginary circle cooperatively defined by the inner free ends of the protrusion tabs 281 is smaller than that of the fixing section 152 of the central tube 15. Then the protrusion tabs 281 are caused to deform due to the urging force exerted thereon by the top end of the fixing section 152 of the central tube 15. Guided by the chamfer 157 of the fixing section 152 of the central tube 15, the protrusion tabs 281 are further deformed until they are moved to a position to enter the engaging slot 155 of the central tube 15. In this state, a bottom of the stator core 22 abuts on the step 159 of the central tube 15. The protrusion tabs 281 resume their original state and engage in the engaging slot 155 of the central tube 15. Thus, the stator 20 is fixed to the central tube 15 firmly.

In the embodiment, the chamfer 157 of the fixing section 152 of the central tube 15 facilitates the assembly of the stator 20 onto the central tube 15. Furthermore, since the protrusion tabs 281 are formed on the upper insulating frame 28, an operator or user can easily check whether the protrusion tabs 281 are engaged into the engaging slot 155 completely to guarantee a good assembly quality of the stator 20 onto the central tube 15.

FIG. 6 shows a fan housing 60 according to an alternative embodiment; the fan housing 60 differs from the fan housing 10 of the previous embodiment in that a central tube 65 of this embodiment is made of plastic material and integrally formed with the base 64 by plastic injection molding. The central tube 65 defines a plurality of elongate engaging slots 655 therethrough along an axial direction of the central tube 65. The engaging slots 655 each extend downwardly from a top end towards a bottom end of the central tube 15. The engaging slots 655 are parallel to and spaced from each other around a circumferential direction of the central tube 65. A width of each engaging slot 655 is substantially equal to that of each of the protrusion tabs 281 of the upper insulating frame 28. In assembly, the protrusion tabs 281 are received and engaged in the engaging slots 655, respectively. The engagement of the protrusion tabs 281 in the spaced engaging slots 655 not only restricts an upward movement of the stator 20 away from the central tube 65, but also a rotation of the stator 20 relative to the central tube 65 along the circumferential direction of the central tube 65.

It is to be understood, however, that even though numerous characteristics and advantages of the disclosure have been set forth in the foregoing description, together with details of the structure and function of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

1. A cooling fan, comprising: a base forming a central tube at a central portion thereof, the central tube defining at least one engaging slot therein; a stator being mounted around the central tube, the stator comprising a stator core, an upper insulating frame being attached to a top side of the stator core and a lower insulating frame being attached to a bottom side of the stator core, the upper insulating frame forming a plurality of protrusion tabs, the protrusion tabs extending inwardly from an inner circumferential surface of the upper insulating frame, the protrusion tabs extending into and engaging in the at least one engaging slot of the central tube; and a rotor being rotatable relative to the stator.
 2. The cooling fan of claim 1, wherein each of the protrusion tabs is substantially trapezoid-shaped.
 3. The cooling fan of claim 1, wherein the stator core comprises an annular body at a central portion thereof, and each of the protrusion tabs comprises an outer end rested on the annular body of the stator core and an inner free end protruding inward beyond the annular body.
 4. The cooling fan of claim 1, wherein the at least one engaging slot comprises a plurality of spaced engaging slots evenly arranged around a circumferential direction of the central tube for receiving the protrusion tabs, respectively.
 5. The cooling fan of claim 1, wherein the at least one engaging slot is annular and defined at a top end of central tube around a circumferential surface of the central tube.
 6. The cooling fan of claim 1, wherein the protrusion tabs are evenly arranged along a circumferential direction of the upper insulating frame.
 7. The cooling fan of claim 1, wherein a chamfer is formed at a top end of the central tube, and the at least one engaging slot is defined under the chamfer.
 8. The cooling fan of claim 1, wherein the central tube comprises a fixing section and a main section located at a bottom end of the fixing section, the main section has a diameter greater than that of the fixing section, whereby a step is formed between the fixing section and the main section, and a bottom of the stator core abuts on the step.
 9. The cooling fan of claim 8, wherein the central tube is made of metal, the central tube further comprises a securing section located at a bottom end of the main section, a top flange and a bottom flange extend outwardly from top and bottom ends of the securing section, respectively, and a portion of the base extending into a space between the top and bottom flanges to engage with the securing section.
 10. A cooling fan comprising: a fan housing having a base and a tube extending upwardly from a center of the base of the fan housing; a stator securely mounted around the central tube, having a lower insulating frame, a stator core on the lower insulating frame and an upper insulating frame on the stator core, a stator coil winding on the lower and upper insulating frame, wherein the upper insulating frame having a protruding tab extending and engaging in a slot defined in the central tube; and a rotor rotatably mounted on the central tube. 